Long-Term Rearing of Medaka Aboard ISS to Clarify the Trans-Generation Effects in Vertebrates Induced by Cosmic Ray Irradiation

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The effect of cosmic ray irradiation on astronaut health is a major problem to be addressed in the near future, however, it is not clear whether or not long-term irradiation of cosmic ray has trans-generation effects on astronauts. JAXA is developing an AQuatic Habitat system (AQH) that will enable us to keep more than 10 medaka adult fishes for three months on the ISS and we are going to investigate the effects of long-term cosmic ray irradiation on the genomes of vertebrate male germ cells using medaka. Transgenic (TG) medaka males that produce three-color fluorescent sperm are being produced. Cosmic-ray irradiation would induce deletion type DNA lesions and a sperm would lose fluorescence if the deletion occurs in the transgenes in the sperm genome. Because a male produces more than 100 million sperm, we can expect to investigate more than 300 million locus in germ cell genomes per one male fish and will be able to clarify whether long-term cosmic-ray irradiation aboard the ISS would induce serious effects on the vertebrate germ genomes or not and also whether micro gravity on the ISS would enhance mutation in vertebrate germ genomes. The first flight of the TG medaka fishes to the ISS will be in 2012 and will bring us the first data of the effects of long-term cosmic-ray irradiation on vertebrate germ genomes.